1. Field of the Invention
The present invention relates to hand tools and more particularly, to a tool shaft and tool bit arrangement.
2. Description of the Related Art
FIGS. 1A and 1B show a tool shaft and tool bit arrangement for use in a detachable screwdriver. According to this design, the shaft 10 has a hexagonal rear coupling rod 11 for coupling to a handle (not shown), a hexagonal front coupling hole 12, a locating groove 13 extending around the periphery near the front end, two tapered through holes 14 formed in the locating groove 13 in communication with the hexagonal front coupling hole 12 at two sides, two steel balls 15 respectively mounted in the tapered through holes 14, and a clamp 16 fastened to the locating groove 13 to hold down the steel balls 15. When the tool bit 1 is inserted into the hexagonal front coupling hole 12, the clamp 16 imparts a pressure to the steel balls 15 against the periphery of the tool bit 1, thereby securing the tool bit 1 firmly to the tool shaft 10. This arrangement is still not satisfactory in function. Because the tool shaft 10 is a solid shaft, it has no room for storing tool bits. Further, when the clamp 16 starts to wear after a long use, the tool bit 1 may slip from the steel balls 15.